The invention relates to a device for the stable holding of a thin-walled hollow metal cylinder by supplying a pressure medium into its inner space. The hollow cylinder is supported at its ends on the perimeter of two centering flanges.
Thin-walled hollow metal cylinders are used for various purposes such as, for example, for the production of pattern master stencils for electroplating or for printing patterns in the printing technology. The expression "thin-walled hollow cylinder" as used herein means a hollow metal cylinder with a wall thickness in the range of about 0.07 to about 0.7 millimeters. Although such cylinders have a relatively high rigidity of their own, this is insufficient for certain working of the outside surface, such as for example a mechanical or photographic patterning. For such working it is known to increase the rigidity by locating inside the hollow metal cylinder a rubber hose which can be sufficiently inflated by a pressure medium that it presses against the inner wall of the hollow cylinder to stress it for giving it the increased rigidity. The thin-walled metal cylinder is centered at its two ends by two centering flanges which are arranged on a support. Between these centering flanges there is a rubber hose which is inflatable by a pressure medium. The ends of the hose are mounted in a pressure-tight seal on a flange, and the hose expands radially to press against the hollow cylinder. The expansion for this is sufficient that the diameter, or circumference, required for treating the outer surface of the hollow cylinder is obtained.
The rubber hose referred to above nevertheless has a number of disadvantages. In order for the hollow metal cylinder to take on a cross-section which is as nearly circular as possible, the expanding of the inflatable rubber hose must be as uniform as possible, something which can be achieved only with great difficulty, and hence is accordingly costly. Since, usually, the length of such hollow cylinders is between about 1.0 and 4.0 m (meters), and the corresponding rubber hoses are not significantly shorter, it is necessary to provide support rings in the inner space of the hollow cylinder to prevent sagging. These rubber hoses are a problem, particularly in the use of a damaged hollow cylinder, such as one having a tear at the edge; these are torn into two or more pieces, because the stressing force is maintained by the rubber hose. After the bursting of the metal cylinder, the rubber hose locally overexpands, which decreases its further usefulness. Aside from this, such a rubber hose of a particular length is useful for various diameters, but only for a particular length of the hollow cylinder, so that there must be available a number of hoses corresponding to the used cylinder length.
It is an object of the invention to provide a device of the type described above and so designed that the disadvantages of the known types are avoided and that it is possible by simple handling and with this same device to make an adaptation for the particular length of the hollow cylinder to be held.